UserDataKey

A UserDataKey is used to declare a key for attaching data to a Object using cogl_object_set_user_data.

The typedef only exists as a formality to make code self documenting since only the unique address of a UserDataKey is used.

Typically you would declare a static UserDataKey and set private data on an object something like this:

static CoglUserDataKey path_private_key;

static void
destroy_path_private_cb (void *data)
{
  g_free (data);
}

static void
my_path_set_data (CoglPath *path, void *data)
{
  cogl_object_set_user_data (COGL_OBJECT (path),
                             &private_key,
                             data,
                             destroy_path_private_cb);
}